The present invention relates to the detection of signals and is more particularly, although not exclusively, concerned with the detection and characterisation of signals relating to the operation of types of equipment using spectral analysis.
In “EMI-Debugging of Complex Systems using different time, modulation, STFFT and Frequency Domain Signal Analysis Techniques” by Zhe Li and David Pommerenke of the Electromagnetic Compatibility Laboratory, Department of Electrical and Computer Engineering, University of Missouri—Rolla, Rolla, MO65409, USA, the application of signal analysis techniques for identifying radiated emission sources is discussed.
In particular, signal analysis techniques that span the time domain via the intermediate modulation and short-term fast Fourier transform (STFFT) domain to the frequency domain are disclosed which provide spectral analysis of equipment of interest, for example, switched power supplies.
In “A New Solution for Signal Intelligence” by James Pierson and Joseph Kovacs of National Instruments, spectrum monitoring and signal intelligence is used to collect and analyse data from communications or other electronic sources to provide data relating to a particular area of interest. Apparatus is disclosed that allows a user to monitor multiple frequency ranges simultaneously by logging data for real-time evaluation and later processing. Processed data can then be compared with stored data to classify the detected signal(s).
In each of the cases discussed above, only spectral analysis of the detected signal(s) is carried out and there is no determination of the modulation on the frequency peaks within the generated spectrum. Information relating to the modulation of the signals at the frequency peaks provides data that is unique to particular modes of operation of types of the equipment being monitored.